In a conventional communication system, when a signal carrying a certain number of information bits representing data is transmitted to a receiving device over a communication channel, the signal is contaminated by channel noise and/or interference from another signal, which may be referred to as an interference signal. If the signal is to be successfully received at the receiving device in the presence of noise as well as the interference signal, the transmit signal has to be strong enough to overcome both the noise and the interference.
Conventional communication systems simply transmit the transmit signal at a power level that is high enough to overcome the noise as well as the interference signal. However, an increase of signal power may be wasteful. Another proposed solution is based on vector modulation in order to implement what is known as Dirty Paper Coding (DPC).
DPC provides, in theory, that if an interference signal is known to the transmitter non-causally, it is possible to devise an encoding scheme that can deliver the desired signal to the intended receiver as efficiently, in terms of the power required to achieve error-free delivery, as in the case where the interference signal does not exist. In other words, DPC provides that in a communication channel with a constraint on the transmit energy and in which the received signal is corrupted by channel noise as well as an interference signal, non-causally known to the transmitter, it is possible to construct a coding scheme such that the error performance of the system would be similar to the error performance of the system in the absence of the interference signal.